Test Your Riflescope Without Firing a Shot

If your rifle is parking bullets all over the page, how do you identify the cause? Is it the barrel, the ammunition, the stock, the trigger, the bedding screw tension — or the scope? 

This question arose for me and Chase Fly during our filming of 30-06 Week. Most of the rifles we were shooting were not printing small 3-shot groups. Some were shockingly wide. Was it the scope? 

We mounted each Maven in Talley Rings, among the most precise in the business.

We had a hard time believing that because the Maven RS1.2 2.5-15x44 scope ($1,200) is a premium build. And we had four of them, all new out of the box. They looked, felt, and adjusted smoothly and precisely. Crisp, 1/4 MOA click adjustments with no backlash. Smooth power adjustments, clean parallax adjustments, and a bright, sharp image at all power settings with no apparent color fringing thanks to Extra Low Dispersion lenses. Surely they couldn’t be malfunctioning, could they? 

The RS1.2 scopes looked, felt, and moved as if precision were the name of the game.

We really began to wonder when the Christiansen Arms Ridgeline FFT, MSRP $2,049.99, shot poorly. We swapped its scope for one that had been on a Browning BLR lever action that had turned in some sub MOA groups. That didn’t change anything. So we were confident the scopes were working well. Nevertheless, many viewers postulated the Mavens were the problem, so I clamped one atop my old custom M70 and put it through its paces, as shown in the attached video. 

The same Maven scope that guided our Browning BLR to sub-MOA groups was tested on the misbehaving Christiansen Arms rifle. The scope was not the problem.

Despite the high-end Maven scope, some of our 30-06 test rifles printed 3-shot groups that looked more like shotgun patterns. Was the rifle, ammo, or scope at fault?

I figured my reliable old M70 custom would be the perfect advanced test platform for one of the Maven RS1.2 scopes, but with the factory ammo used, groups were still large enough to make reticle adjustments questionable.

What you see me doing in this video is something you can easily do with your scopes to test their function without having to fire expensive ammunition. Basically you are watching the reticle move as you adjust the turrets. Ideally this would be done with the scope locked to a solid platform that eliminates any movement other than the reticle’s. But, as I did in this video, you can prop the rifle firmly and dial the turrets carefully to get a pretty solid reading on its accuracy. 

What’s happening when you dial a turret down is the reticle moves up. When you dial right, it moves left and vice versa. All you have to do is watch these movements across a 1-inch grid target. So, set the scope with the reticle centered on one the of a grid square junctions. Then carefully, without moving the rifle/scope, dial 4 clicks and watch to see if the reticle moves one square. Dial another four clicks. Did the reticle move another square over? It should have. Dial back eight clicks and the reticle should return to where you started. With this process you can dial as many inches or MOAs as you care to test. I went as far as 12 MOA up and 10 left during my test and the reticle appeared to move precisely there. My subsequent shot came within about 1.25-inches of that spot. 

This is the “trouble” with shooting to confirm scope function. You can’t always KNOW that the rifle or that particular bullet wasn’t a flier or didn’t land at an extreme edge of its grouping average. If you have an “old reliable” with time tested ammo you can trust, shooting after scope adjustments does work, but, as you can see in this video, even with my normally sub MOA M70, the factory ammo I was shooting sometimes threw a flier. I honestly do not know if those were the fault of the ammo or if something is changing in the rifle, but that’s another reason why testing a scope’s function visually is advised. 

A target with one-inch grids is perfect for testing the movements of a scope’s reticle.

The Maven RS1.2 scopes included an adjustable illuminated reticle, a side-focus parallax adjustment dial, and of course MOA turret dials.

Another visual function test involves the power dial. Some cheap scopes will change the position of the lenses/sight picture in relation to the reticle as the power ring moves internal lenses to change the magnification. If the system isn’t concentric, the aim point can shift slightly. Test this by locking the scope on a grid corner, then watching as you dial the power down. This gets challenging at lower powers because the aiming point gets hard to see, so take your time and do it again and again until you’re satisfied. Of course, you can double check this by shooting at various power settings, but you’re again at the mercy of your rifle/ammo group variability. 

The issue of a sticking erector tube can also be assessed without shooting. Again position the scope on a grid corner. Dial several MOAs and watch. If the reticle doesn’t move, it’s obviously stuck on something, most likely the turret post that’s touching it. Turret posts are always in contact with the erector tube, but so are the springs countering them. This spring or springs (some scopes have one, some two, some four) could also be sticking. Regardless, you’ll see the effect in the eyepiece as you dial. 

While I was testing/dialing the Maven in this video, I clearly saw that the reticle moved appropriately. Sadly, this incriminated either my shooting ability, the ammo we were using, or the rifles. I was judging my performance closely and critically and can’t honestly say I was at fault, although sometimes my bench set up might get some blame. Loose tripod, drag between the stock and bags, perhaps a sling stud catching the bag. My educated guess is that the factory ammo just wasn’t matching well with any of the rifles, although with 12 different rifles, that seems a bit crazy, too, especially when you consider the better groups Chase and I recorded during our 308 Week testing of 10 rifles chambered 308 Winchester. 

The fact that some of the tested rifle turned in some stellar groups indicated the scope’s weren’t the source of any inaccuracy issues.

This calls up another question: is the 308 Winchester cartridge inherently more accurate than the 30-06, as many claim? To a tiny degree it probably is, but as I’ve always said, not appreciably for hunting applications. What seems more likely to me is that 308 chambers are reamed more carefully or precisely on average (because so many 308 Win. rifles are destined to be build for target shooting) and 308 ammunition is similarly more carefully loaded. The older 30-06, generally seen as a run-of-the-mill hunting rifle, is perhaps more casually built with looser tolerances, perhaps on the large end of the scale. Similarly, 30-06 ammo, since it might be used in rifles built as far back as 1906, is built at the narrow end of the tolerance window. The result is an unusually loose fit and less than stellar accuracy.  

Despite what so many claim about their rifles’ accuracy, a sub-MOA group is not easy to shoot consistently.

Even if this is the case and the 30-06 isn’t an inherently less accurate cartridge design than the 308 Winchester, the practical reality is that the average factory rifle shooting factory ammunition will likely be more accurate in 308 Winchester than 30-06. 

So much to test, so much to consider! But at least we can now test our scopes for accuracy without having to fire dozens of rounds of expensive ammunition.